What do you mean by the term "unlocked"?
Normally when someone uses the term "unlocked", it means to make it able to use a non-Verizon SIM card in it to use on carriers outside of the Verizon network, such as foreign countries. Verizon does not "unlock" the iPhone 4 as it does not utilize a SIM card in the phone.
On the Verizon network, SIM cards were used in iPhone models starting with the iPhone 4S. Verizon will unlock an iPhone 4S if it is active on a Verizon line of service which has been in good standing for the last 60 days.
With the Verizon iPhone 5, it comes unlocked.